(a) Field of the Invention
The present invention relates to a fabric for an airbag and a method of preparing the same, and particularly to a fabric for an airbag that includes a polyester fiber having low modulus, high strength, and high elongation, and has superior mechanical properties, such as toughness, tearing strength, and the like, a method of preparing the same, and an airbag for a car including the same.
(b) Description of the Related Art
Generally, an airbag is an apparatus for protecting a driver and passengers by providing a gas into the airbag by exploding gunpowder so as to inflate the airbag after detecting a crash impact with an impact detecting sensor, when a driving car collides at a speed of about 40 km/h or more.
Characteristics required of the fabric for an airbag are low air permeability for unfolding the airbag well at the time of collision, high strength and high heat resistance for preventing damage to and rupture of the airbag itself, and flexibility for reducing the impact provided to occupants.
Particularly, the airbag for a car is prepared in a certain shape and installed in a steering wheel, door roof rails, or side pillars of the car in a folded form so as to minimize its volume, and it is expanded and unfolded when an inflator operates.
Therefore, it is very important that the airbag has folding properties and flexibility for reducing the shock to the occupant in addition to good mechanical properties of the fabric for maintaining the folding and packaging properties of the airbag effectively when it is installed in a car, preventing damage to and rupture of the airbag itself, providing good unfolding properties of the airbag cushion, and minimizing the impact provided to the occupant. However, an airbag fabric that can maintain superior air-tightness and flexibility for the occupant's safety, sufficiently endure the impact applied to the airbag, and be effectively installed in a car has not yet been suggested.
Previously, a polyamide fiber such as nylon 66 has been used as the raw material of the fiber for an airbag. However, nylon 66 has superior impact resistance but is inferior to polyester fiber in humid heat resistance, light resistance, and shape stability, and is expensive.
Meanwhile, Japanese patent publication No. Hei 04-214437 suggested a polyester fiber for reducing such defects. However, when the airbag was prepared by using a prior polyester fiber, it was difficult to install in a narrow space in a car because of its high stiffness, excessive thermal shrinkage was caused by a heat-treatment at a high temperature due to its high modulus and low elongation, and there was a limitation for maintaining sufficient mechanical and unfolding properties in severe conditions of high temperature and high humidity.
Therefore, it is needed to develop a fabric that maintains superior mechanical properties and air-tight effect so as to be used as an airbag fabric for a car, and also maintains flexibility for reducing the impact applied to occupants, the packing properties, and superior mechanical properties in the severe conditions of high temperature and high humidity.